Corrosion of water conduits in office buildings

Transcription

1 Emission estimates for diffuse sources Netherlands Emission Inventory Corrosion of water conduits in office buildings Version dated June 2008 NETHERLANDS NATIONAL WATER BOARD - WATER UNIT in cooperation with DELTARES and TNO

2 Corrosion from water conduits in office buildings 1 Description of emission source Emissions described in this factsheet are copper emissions due to the corrosion of drinking water conduits in commercial buildings (offices). The copper content of drinking water pipes is higher than the original level in the water supply by three causes: the flow of water through the pipes, water standing in the pipes, and heating in boilers and geysers. This fact sheet deals with all these causes together. The corrosion of drinking water pipes in residential dwellings is part of the domestic waste water system (see the fact sheet on Domestic Waste Water [13]), and is not covered here. This emission source is attributed to the governmental target sector Trade and services. 2 Explanation of calculation method Emissions are calculated by a simple method which involves multiplying an activity rate (AR), in this case the area of office space in the Netherlands, by an emission factor (EF) per substance, expressed in emission per AR unit. This method of calculation is explained in detail in the Guide to the Regional approach to diffuse sources [2]. The calculation method for emissions from this emission source is described in further detail in the water system survey of construction materials [15] and is largely based on Van Oppen's work [14]. The emission calculated in this way is referred to as the total emission. 3 Activity rates Information on the area of build-up area with offices in the Netherlands is taken from statistics produced by Statistics Netherlands. The figures are based on the total area of all types of offices: socio-cultural facilities, other public facilities and the service sector (categories 16, 17 and 20 respectively). The total area in 1989 was x 10 8 m 2. This figure was subsequently converted in the light of the increase in area used for the second environmental report [12] to give a figure for 1990 of 3.41 x 10 8 m 2. In the absence of any later data from Statistics Netherlands, figures for subsequent years are based on the growth trends in industrial premises areas shown in the European Renaissance scenario in the second environmental survey, which pointed to growth of 1.2% a year between 1990 and 2006 [12]. Table 1: Trend in the AR, the area of office buildings in the Netherlands Building-up area with offices (m 2 ) Reference ,300,000 [11], page ,000,000 [12], page 28 and [13] ,280,000 [12], page 28 and [13] ,460,000 [12], page 28 and [13] ,920,000 Estimate, + 1.2%/year ,380,000 Estimate, + 1.2%/year ,472,000 Estimate, + 1.2%/year 4 Emission factors The emission factor for copper is derived from [15], taking account of softening of drinking water, i.e. the percentage of drinking water deliberately softened by water supply companies. This is because the rate of corrosion of water pipes is significantly affected by the proportion of drinking water that is softened; the more water is softened, the slower the rate of corrosion and the less 2

3 copper is dissolved in the drinking water. A softening factor has been worked out to take account of partial softening (see section 5 below). An emission factor for 1993 has been calculated on the basis of [15]: the combined contact surface area of copper water pipes for residential and commercial/industrial buildings is 10.6 million m 2. The figure for residential dwellings alone is 9.2 million m 2, leaving 1.4 million m 2 for commercial/industrial buildings. Combined copper emissions for residential dwellings and commercial/industrial buildings is 101,000 kg of copper, which means that the emission figure for commercial/industrial buildings can be calculated as 13,300 kg of copper (= 1,400,000/1,0600, ,000). The emission factor for commercial/industrial buildings in 1993 is then worked out by dividing 13,300 kg of copper by 353,280,000 m 2 of commercial office space, giving a result of 37.6 mg Cu/m 2 of office space per year. The softening factor is applied to correct the emission factor. The emission factors are expressed as mg/m 2 office buildings/year. Table 2: Emission factor trends: mg copper/m 2 office buildings/year Emission factor As water hardness affects the emission of copper from pipes (the lower the hardness, the less copper is emitted), this aspect is taken into account by means of a softening factor. The softening factor is calculated in [15] as: (y-x) Where: x = the fraction of softened water in 1985 and y = the fraction of softened water in year y. The table below shows the fractions of softened water reported for individual years (figures obtained from the Dutch association of drinking water companies, VEWIN [17]). The calculated softening factors are also given for the years in question. The softening factors have been used to work out the emission factors for 1985, 1990, 1993, 1995, 2000, 2005 and 2006 (see section 4). Table 3: Summary of percentages of softened water in individual years Percentage of softened water Softening factor (%) From 2000 onwards no data is available on the percentage of drinking water actively softened by water supply companies. It is assumed that this figure has been rising by 1% a year since 1995 (similar to the trend in previous years), meaning that in % of drinking water was softened. 5 Effects of policy measures Water supply companies have been increasing the extent of drinking water softened. This was taken into account in the calculation of the emission factor. 3

4 6 Emissions calculated The table below shows copper emissions caused by the corrosion of water pipes in office buildings. The emissions are calculated by multiplying the activity rate (the area of office space in the Netherlands in the year in question) by the emission factor (the corrosion of copper water pipes in office buildings ea ch year). Table 4: Emission of copper (tonnes/year) as a result of corrosion of water pipes in office buildings Copper emission (tonnes/year) 'Release into environmental compartments All emissions caused by the corrosion of water pipes in office buildings enter the sewers (indirect emissions). 8 Description of emission pathways to water Emissions into water arise indirectly as a result of emissions from the sewer system, combined sewer overflows, and effluents from urban waste water treatment plants. The fact sheet "Effluents from waste water treatment plants and sewer systems" [8] describes this in further detail. 9 Spatial allocation The spatial distribution of emissions is assigned on the basis of a set of digital maps held by the Netherlands Environmental Assessment Agency (PBL) drawn up using emission records. These maps present the spatial distribution of all kinds of parameters throughout the Netherlands, such as population density, traffic intensity, area of agricultural crops, etc. For the purposes of emission registration these maps are used as 'locators' to determine the spatial distribution of emissions. The range of possible locators is limited (see [16] for a list of available locators), as not every conceivable parameter can be used as a locator. In practice the locator judged to be the best proxy of the activity rate of the emission in question is applied for the distribution of emissions. It is assumed that the distribution of emissions throughout the country is proportional to the national distribution of the locator. The table below shows the locator used for the spatial allocation of the various emission sources. Table 5: Summary of spatial allocation method Element Corrosion of water pipes in industrial/commercial buildings Locators Number of inhabitants per grid cell measuring 500x500 metres The method used to determine the locators is described in [16]: Number of inhabitants The number of inhabitants per grid cell measuring 500x500 metres is derived from the MNP's map of grid cell distribution based on the number of inhabitants, residential dwelling units and inhabitants per sewage unit. This map is based on figures produced by Statistics Netherlands (CBS) on numbers of inhabitants and numbers of residential dwelling units in each local authority (for 2005). The distribution of inhabitants among grid cells in a local authority was calculated using the 4

5 comprehensive database of address coordinates in the Netherlands (which contains addresses and types of dwelling unit) and the 2003 sewage unit database. 10 Comments and changes in regard to previous version There have been no changes in the calculation methodology compared to previous publications, such as [15], [2] and [9]. 11 Accuracy and indicated subjects for improvement The method used in the Emission Inventory publications has been followed as far as possible in classifying the quality of information [9]. It is based on the CORINAIR (CORe emission INventories AIR) methodology, which applies the following quality classifications: A: a value based on a large number of measurements from representative sources; B: a value based on a number of measurements from some of the sources that are representative of the sector; C: a value based on a limited number of measurements, together with estimates based on technical knowledge of the process; D: a value based on a small number of measurements, together with estimates based on assumptions; E: a value based on a technical calculation on the basis of a number of assumptions. The emission factors are classified as D; the major point of uncertainty is in determining the percentage of drinking water that is deliberately softened. The activity rate is also based on records and assumptions, and comes into class C. Distribution of emissions among the various components can easily be identified and is logical, and therefore comes into class A. Emission pathways into water are not discussed in this fact sheet, but are classed as C in reference [8]. The spatial allocation of emissions is fairly reliable and classed as C. Element of emission calculation Activity Rates Emission factors Distribution among compartments Emission pathways to water Spatial allocation Reliability class C D A C C The main areas where improvements could be made are: - Improving the quality of information about the activity rate - Improving information about the effects of the influence of water softening on copper corrosion. - Improving data on the percentage of water actively softened by water supply companies. - Investigation into corrosion of substances other than copper from water pipes. 12 Request for reactions Any questions or comments on this working document should be addressed to Richard van Hoorn, Centre for Water Management, +31 (0) , richard.van.hoorn@rws.nl or Joost van den Roovaart, Deltares, +31 (0) , joostvandenroovaart@deltares.nl. 13 References [1] Coppoolse, J. et al., april Zware metalen in oppervlaktewater. Bronnen en maatregelen. SPEED-document [Heavy metals in surface water, sources and measures. SPEED-document]. RIZA notanr , RIVM notanr

6 [2] CIW/CUWVO werkgroep VI, februari Handreiking Regionale aanpak diffuse bronnen. Bijlage 1, par 2.2. [3] CBS. Statistisch jaarboek 1990 [Statistics Netherlands Statistical book]. [4] CBS. Statistisch jaarboek 1996 [Statistics Netherlands Statistical book]. [5] CBS. Statistisch jaarboek 1999 [Statistics Netherlands Statistical book]. [6] CBS. Statistisch jaarboek 2000 [Statistics Netherlands Statistical book]. [7] HASKONING, juni Onderzoek naar emissies uit huishoudens in opdracht van RIZA. [8] Rijkswaterstaat Waterdienst, Effluenten RWZI s, regenwaterriolen, niet aangesloten riolen, overstorten en IBA s, factsheets diffuse bronnen. RWS-WD, Lelystad, juni [9] Most, P.F.J. van der, van Loon, M.M.J., Aulbers, J.A.W. en van Daelen, H.J.A.M., juli Methoden voor de bepaling van emissies naar lucht en water. Publicatiereeks Emissieregistratie, nr. 44. [10] CBS, Bodemstatistiek 1985 [Statistics Netherlands Statistics on Land Use]. [11] CBS, Bodemstatistiek 1989 [Statistics Netherlands Statistics on Land Use]. [12] RIVM, Nationale Milieuverkenning 2, [13] Rijkswaterstaat Waterdienst, Huishoudelijk Afvalwater, factsheets diffuse bronnen. RWS-WD, Lelystad, juni [14] Oppen, P.W. van, Haalbaarheidsonderzoek terugdringing lozing koper en zink uit woningen. Bouwcentrum Advies. [15] Bentum, F. van et al., Watersysteemverkenningen, Doelgroepstudie Bouwmaterialen. RIZA notanr [16] Molder, R. te, Notitie ruimtelijke verdeling binnen de emissieregistratie. Een overzicht. 6